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The Sicily Channel, located in the central Mediterranean Sea, represents a key point for the regional oceanographic circulation, as it is regarded as the sill that separates the western and eastern basins. Therefore, it is regarded as a unique zone in the well-documented west-to-east Mediterranean productivity gradient. Here we present a time series of settling planktonic foraminifera assemblages from November 2013 to October 2014. Altogether, 19 samples from the sediment trap C01 deployed at a water depth of around 400 m have been used. More than 3700 individuals and 15 different species have been identified. Globorotalia inflata, Globorotalia truncatulinoides, Globigerina bulloides, Globigerinoides ruber, and Globigerinoides ruber (pink) were the five main species identified, accounting for more than 85 % of the total foraminifera. The total planktonic foraminifera flux mean value was 630 shells m -2 d -1 , with a minimum value of 45 shells m -2 d -1 displayed during late autumn 2013 and a maximum of 1890 shells m -2 d -1 reached during spring 2014. This is likely due to the regional oceanographic configuration and the marked seasonality in the surface circulation. During spring and winter, Atlantic Water (AW) dominates the surface circulation, bringing cool and nutrient-enriched waters. This results in a planktonic foraminifera flux increase and a dominance of western basin taxa. During summer and autumn, the circulation is dominated by the eastern warm and oligotrophic Levantine water, which leads to a planktonic foraminifera flux decrease and the dominance of eastern basin species. Our comparison with satellite-derived sea surface temperatures (SSTs) and chlorophyll a data showed that G. inflata was associated with cool and nutrient-rich conditions, while both G. ruber morphotypes were associated with warm and oligotrophic conditions. However, no trends were identified for G. truncatulinoides or G. bulloides. As the latter species flux increased coincidently with that of benthic foraminifera, we considered that this species might have a resuspended origin. The comparison of the Sicily Channel data with other Mediterranean time series indicates that the annualized planktonic foraminifera flux was lower than in the westernmost Alboran Sea but higher than in the easternmost Levantine Basin. The Sicily Channel species diversity was the highest among the compared zones, highlighting the influence of the different basins and its transitional aspect from a planktonic foraminifera population perspective. Finally, we compared the settling planktonic foraminifera assemblage with the assemblages from seabed sediment located in the vicinity of the Sicily Channel. The differences in the seabed populations varied according to the sites studied. The deep-dwelling species dominated the settling assemblage samples, while eutrophic and oligotrophic species were more abundant in the sediment. Finally, a high-resolution chronology comparison allowed us to show that this planktonic foraminifera population shift likely developed during the late Holocene prior to the industrial period; however, its causes remain uncertain. [ABSTRACT FROM AUTHOR]

The Sicily Strait, located in the central Mediterranean Sea, represents a key point for the regional oceanographic circulation as it is considered the sill that separates the western and eastern basins. Therefore, it is considered a unique zone regarding the well-documented west-to-east Mediterranean productivity gradient. Here we document the planktic foraminifera assemblages retrieved by the C01 sediment trap between November 2013 and October 2014. 19 samples from the sediment trap deployed at a water depth of around 400 m have been used. More than 3700 individuals and 15 different species have been identified. Globorotalia inflata , Globorotalia truncatulinoides , Globigerina bulloides , Globigerinoides ruber and ruber (pink) were the five main species identified, accounting for more than 85 % of the total foraminifera. The total planktic foraminifera flux mean value was 630 shells m-2 d-1, with a minimum value of 45 shells m-2 d-1displayed during late autumn 2013 and a maximum of 1890 shells m-2 d-1 reached during spring 2014. Most of the species fluxes followed a similar pattern. This is likely the result of the regional oceanographic configuration and the marked seasonality in the surface circulation. During spring and winter, the Atlantic waters dominate the surface circulation, bringing cool and nutrient enriched waters. This results in a planktic foraminifera flux increase and a dominance of western basin taxa. During summer and autumn, the circulation is dominated by the eastern warm and oligotrophic Levantine water, which results in planktic foraminifera flux decrease and the dominance of easter basin species. Our comparison with satellite derived SST and chlorophyll- a data showed that G. inflata was associated with cool and nutrient rich conditions, while both G. ruber morphotypes were associated with warm and oligotrophic conditions. However, no trends were identified for G. truncatulinoides or G. bulloides. In addition, a comparison of the Sicily Strait data with other Mediterranean time series located in the Alboran Sea, Gulf of Lions and the Levantine basin was carried out. Our data indicated that the annualized planktic foraminifera flux was lower than in the westernmost Alboran Sea but higher than in the easternmost Levantine basin. However, the Sicily Strait species diversity was the highest among the compared zones, highlighting the influence of the different basins and its transitional aspect from a planktic foraminifera population perspective. Finally, we compared the sediment trap planktic foraminifera assemblage with the assemblages from seabed sediment located in the vicinity of the Sicily Strait. Our results showed that the sediment trap population significantly differed from the assemblages in the seabed sediment. The deep-dwelling species dominated the sediment trap samples, while eutrophic and oligotrophic species were significantly more abundant in the core-tops, highlighting a potential effect of the recent Mediterranean environmental change, such as warming and a potential shift in the oceanographical conditions on the planktic foraminifera population. [ABSTRACT FROM AUTHOR]

The Mediterranean Sea sustains a rich and fragile ecosystem currently threatened by multiple anthropogenic impacts that include, among others, warming, pollution, and changes in seawater carbonate speciation associated to increasing uptake of atmospheric CO 2. This environmental change represents a major risk for marine calcifiers such as planktonic foraminifera, key components of pelagic Mediterranean ecosystems and major exporters of calcium carbonate to the sea floor, thereby playing a major role in the marine carbon cycle. In this study, we investigate the response of planktic foraminifera calcification in the northwestern Mediterranean Sea on different timescales across the industrial era. This study is based on data from a 12-year-long sediment trap record retrieved in the in the Gulf of Lions and seabed sediment samples from the Gulf of Lions and the promontory of Menorca. Three different planktic foraminifera species were selected based on their different ecology and abundance: Globigerina bulloides, Neogloboquadrina incompta, and Globorotalia truncatulinoides. A total of 273 samples were weighted in both sediment trap and seabed samples. The results of our study suggest substantial different seasonal calcification patterns across species: G. bulloides shows a slight calcification increase during the high productivity period, while both N. incompta and G. truncatulinoides display a higher calcification during the low productivity period. The comparison of these patterns with environmental parameters indicate that controls on seasonal calcification are species-specific. Interannual analysis suggests that both G. bulloides and N. incompta did not significantly reduce their calcification between 1994 and 2005, while G. truncatulinoides exhibited a constant and pronounced increase in its calcification that translated in an increase of 20 % of its shell weight. The comparison of these patterns with environmental data reveals that optimum growth conditions affect positively and negatively G. bulloides and G. truncatulinoides calcification, respectively. Sea surface temperatures (SSTs) have a positive influence on N. incompta and G. truncatulinoides calcification, while carbonate system parameters appear to affect positively the calcification of three species in the Gulf of Lions throughout the 12-year time series. Finally, comparison between sediment trap data and seabed sediments allowed us to assess the changes of planktic foraminifera calcification during the late Holocene, including the pre-industrial era. Several lines of evidence indicate that selective dissolution did not bias the results in any of our data sets. Our results showed a weight reduction between pre-industrial and post-industrial Holocene and recent data, with G. truncatulinoides experiencing the largest weight loss (32 %–40 %) followed by G. bulloides (18 %–24 %) and N. incompta (9 %–18 %). Overall, our results provide evidence of a decrease in planktic foraminifera calcification in the western Mediterranean, most likely associated with ongoing ocean acidification and regional SST trends, a feature consistent with previous observations in other settings of the world's oceans. [ABSTRACT FROM AUTHOR]

The aim of this work is to investigate the variability of planktic foraminifera calcification in the northwestern Mediterranean Sea on seasonal, interannual and pre-industrial Holocene time scales. This study is based on data from a 12-year-long sediment trap record retrieved in the in the Gulf of Lions and seabed sediment samples from the Gulf of Lions and the promontory of Menorca. Three different planktic foraminifera species were selected based on their different ecology and abundance: Globigerina bulloides, Neogloboquadrina incompta , and Globorotalia truncatulinoides. A total of 273 samples were weighted in both sediment trap and seabed samples. As the traditionally used sieve fractions method is considered unreliable because of the effect of morphometric parameters on the foraminifera weight, we measured area and diameter to constrain the effect of these parameters. The results of our study show substantial different seasonal calcification patterns across species: G. bulloides showed a slight calcification increase during the high productivity period, while both N. incompta and G. truncatulinoides display a higher calcification during the low productivity period. The comparison of these patterns with environmental parameters revealed that Optimum Growth Conditions temperature and carbonate system parameters are the most likely to influence seasonal calcification in the Gulf of Lions. Interannual analysis suggest that both G. bulloides and N. incompta slightly reduced their calcification between 1994 and 2005, while G. truncatulinoides exhibited a constant and pronounced increase in its calcification that translated in an increase of 20 % of its shell weight for the 400–500 µm narrow size class. While our data suggest that carbonate system parameters are the most likely environmental parameter driving foraminifera calcification changes over the years. Finally, comparison between sediment trap data and seabed sediments allowed us to assess the changes of planktic foraminifera calcification during the late Holocene, including the preindustrial era. Several lines of evidence strongly indicate that selective dissolution did not bias the results in any of our data sets. Our results showed a clear calcification reduction between pre-industrial Holocene and recent data with G. truncatulinoides experiencing the largest calcification decrease (32–40 %) followed by N. incompta (20–27 %) and G. bulloides (18–24 %). Overall, our results provide evidence of clear reduction in planktic foraminifera calcification in the Mediterranean most likely associated with ongoing ocean acidification and consistent with previous observations in other settings of the world's oceans. [ABSTRACT FROM AUTHOR]